Problem bleeding baseboard heater


Old 11-10-13, 09:03 AM
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Problem bleeding baseboard heater

I recently removed the baseboard heater in my bathroom to do work on the floor and wall. I put it back in place and turned the boiler on, bleeding the air out of the baseboard heater unit until a steady stream of water was coming out. The unit heated up and I closed the bleeder valve.

A few hours later I noticed that the baseboard heater unit was cold. I opened the bleeder valve and a steady stream of cool water came out for a few minutes, then it became hot and the unit heated up. I closed the bleeder valve. A few hours later, it was cold again even though the system was continuously running.

After trying this a few times, it was the same. The unit will heat up within minutes while the bleeder valve is open but cools within minutes as soon as the valve is closed.

There is only one loop and this is the only unit not working. I believe it is a monoflow system.

I increased the pressure by pulling up on the lever atop the pressure regulator and bled it for about 15 minutes that way but it did not help. I stopped because the additional pressure was making the pressure relief valve leak and groan. I didn't want to blow it.

The increased pressure did not fix the problem. It will heat in minutes while the bleeder valve is open water is streaming out but cools off almost immediately after closing the bleeder valve.

Any ideas?
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Old 11-10-13, 01:19 PM
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Damn monoflos... what a pita to get them to bleed!

You are bleeding with the system pump running?

Try it again after shutting off the system for about a half hour and system pump NOT running. Jack the pressure in the system as high as possible without opening the relief valve before bleeding. Hopefully the air bubble will move under the bleeder.

Bleeder should be on DOWNSTREAM end of baseboard, is it?

Part of the problem is that those little pee-hole bleeders don't move enough volume to get the air bubble to move. That and the fact that it's monoflo means that you have water pressure on BOTH sides of the baseboard and the bubble could be 'stuck' at the end opposite the bleeder.

Is end of baseboard with bleeder HIGHER than end without?

If not, is it possible to raise one end (enough slack in pipes?) so that it IS higher?

By any chance, are there valves on either or both of the lines coming off the tees? Or possibly a valve BETWEEN the two tees?
Old 11-17-13, 10:12 AM
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Those were good suggestions and I tried them, but they didn't work. I think I just found out why.

As I was working on it I realized that the return is heating up before the supply. My valve is stuck closed. The knob turned to the on position and as I played with it, it just kept turning. Then I tried to close it and it just kept turning...the knob is stripped and the valve is stuck in the closed position.

I'm going to cut the valve out and replace it...


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